KR101815981B1 - Conductive fim and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a conductive composite film which includes a flexible substrate; a polymer layer formed on the flexible substrate; and a corrugated conductive nanowire including peaks and valleys formed on the polymer layer. The conductive composite film of the present invention may include a corrugated conductive nanowire having peaks and valleys formed by a buckling phenomenon, thereby improving flexibility, reducing a change in conductivity due to flexibility, and improving mechanical properties. In addition, a method for manufacturing a conductive composite film according to the present invention can induce the buckling phenomenon using a pre-strained flexible substrate, thereby selectively buckling conductive nanowires, so that the transparency of the conductive composite film can be excellent.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a conductive composite film,

The present invention relates to a conductive composite film and a method of manufacturing the conductive composite film, and more particularly, to a conductive composite film including corrugated conductive nanowires having a corrugated structure formed by buckling, and a method of manufacturing the conductive composite film.

2. Description of the Related Art As electronic devices are widely used, there is a growing demand for flexible electronic devices capable of overcoming the limitations of conventional electronic devices on a rigid substrate. Electronic devices used in fields such as flexible displays, smart garments, dielectric elastomer actuators (DEA), biocompatible electrodes, in vivo electrical signal sensing, etc., require flexible and stretchable forms. One of basic and important technologies in the field of electronic devices having such flexibility and stretchability is to form electrodes that can be stretched while maintaining conductivity.

Materials such as metals are excellent in conductivity, but are difficult to use due to their rigid and stiff nature. When using materials such as carbon nanotubes and graphene alone, it is also difficult to make stretchable electrodes.

Examples of a method for making stretchable electrodes include a method in which carbon nanotubes are mixed with a transparent fluorinated polymer and an ionic liquid to form a paste, an example in which a mixture of metal particles and polyacrylic acid is made into a paste to form a pattern by an ink jet method, There has been reported an example in which a metal layer is formed on a PDMS substrate to make it stretchable as the wrinkles expand. However, these methods have problems in that the materials used or the corrugated substrate are not very stretchable so that the conductivity is sharply lowered or mechanically broken according to expansion and contraction.

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a conductive composite including a conductive nanowire having corrugations and valleys formed by buckling to improve elasticity, Film.

Another object of the present invention is to provide a method for manufacturing a conductive composite film having a conductive film by selectively buckling a conductive nanowire by inducing a buckling phenomenon using a pre-strained elastic substrate.

According to an aspect of the present invention,

A stretchable substrate; A polymer layer formed on the stretchable substrate; And a corrugated conductive nanowire including a corrugation and a floor formed on the polymer layer.

The waveform of the conductive nanowire may be formed by buckling.

The buckling phenomenon may occur parallel to the plane direction of the stretchable substrate and along a certain direction.

The modulus of the stretchable substrate may be between 0.01 Mpa and 20 GPa.

The modulus of the polymer layer may be between 0.01 Mpa and 10 GPa.

The stretchable substrate may include at least one selected from the group consisting of polydimethylsiloxane and polyurethane.

The polymer layer may be a block copolymer layer.

The block copolymer layer may be a poly (styrene-isoprene-styrene), a poly (styrene-butadiene-styrene), or a SEBS (poly (styrene- -propylene-styrene)).

The conductive nanowire may include at least one selected from silver, gold, aluminum, copper, platinum, palladium, tin and carbon nanotubes (CNT).

According to another aspect of the present invention,

An electrode comprising the conductive composite film is provided.

According to another aspect of the present invention,

(a) modifying the surface of the wafer with a hydrophilic surface; (b) coating the conductive nanowires on the wafer; (c) coating a solution containing a polymer on the conductive nanowire to prepare a laminate in which a conductive nanowire-polymer composite is laminated on the wafer; (d) preparing a stretchable substrate to which a pre-strain is applied by applying strain to the stretchable substrate on which the polymer is formed; (e) bonding the conductive nanowire-polymer composite contained in the laminate to the polymer contained in the stretchable substrate to which the pre-strain is applied; (f) heat treating the result of step (e); And (g) treating the resultant of step (f) with a polar solvent to separate the wafer from the result of step (f) to produce a conductive composite film according to claim 1. 7. A method for manufacturing a conductive composite film, / RTI >

A buckling phenomenon may occur parallel to the direction in which the strain is applied.

The strain may be smaller than a critical strain of the polymer layer included in the conductive composite film.

The strain may be 0.01 to 1,000%.

In step (a), the surface of the wafer may be treated with an O ₂ plasma to modify it into a hydrophilic surface.

The polar solvent may include at least one selected from water, ethanol, isopropyl alcohol, propanol and butanol.

According to another aspect of the present invention,

A method of manufacturing an electrode including the method of producing the conductive composite film is provided.

The conductive composite film of the present invention may include a conductive nanowire having corrugated and corrugated webs formed by buckling, thereby improving the stretchability, reducing the change in conductivity due to elongation and shrinkage, and improving mechanical properties.

In addition, the method of manufacturing a conductive composite film of the present invention can induce a buckling phenomenon by using a pre-strained stretch substrate to selectively buckle only the conductive nanowires, so that the conductivity of the conductive composite film can be excellent.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart schematically showing a method for producing a conductive composite film of the present invention.
2 schematically shows a method for producing the conductive composite film of the present invention.
3 is an SEM image of a conductive composite film produced according to Example 1 of FIG.
4 is an optical microscope (OM) image after strain is again applied to the conductive composite film produced according to Example 1. Fig.
FIG. 5 shows the result of measuring the change in resistance while applying the strain again to the conductive composite film produced according to Example 2. FIG.
FIG. 6 shows the results of measurement of the transmittance of the silver nanowire-coated film produced according to Preparation Example 1 and the conductive composite film (red) prepared according to Examples 1 to 3.
7 is an SEM image of the conductive composite film produced according to Production Example 2 and Example 4. Fig.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

However, the following description does not limit the present invention to specific embodiments. In the following description of the present invention, detailed description of related arts will be omitted if it is determined that the gist of the present invention may be blurred .

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises ", or" having ", and the like, specify that the presence of stated features, integers, steps, operations, elements, or combinations thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, or combinations thereof.

Hereinafter, the conductive composite film of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

The conductive composite film of the present invention comprises a flexible substrate; A polymer layer formed on the stretchable substrate; And a corrugated conductive nanowire including a valley and a floor formed on the polymer layer.

The waveform of the conductive nanowire may be formed by buckling.

The buckling phenomenon may occur parallel to the plane direction of the elastic substrate and along a certain direction, and the closer the angle of the constant direction is to 90 °, the smaller the influence of the buckling phenomenon may be. Accordingly, as the arrangement of the conductive nanowires coincides with the predetermined direction, the influence of the buckling phenomenon can be increased, which is desirable.

The stretchable substrate may be made of polydimethylsiloxane, polyurethane, or the like, but is not limited thereto. Any transparent and stretchable substrate can be used.

The modulus of the stretchable substrate may be 0.01 Mpa to 20 Gpa, preferably 0.1 Mpa to 1 Gpa, and more preferably 1 Mpa to 100 Mpa.

The polymer layer may be a block copolymer layer which is easily modulated. The block copolymer layer may be formed of a material selected from the group consisting of SIS (styrene-isoprene-styrene), SBS (poly (styrene-butadiene-styrene) -propylene-styrene), and the like. The modulus of the block copolymer layer may be 0.01 Mpa to 10 GPa, preferably 0.1 Mpa to 9 GPa, and more preferably 1 Mpa to 8 GPa.

The conductive nanowire may include silver, gold, aluminum, copper, platinum, palladium, tin, carbon nanotubes (CNT), and the like, preferably silver nanowires.

FIG. 1 is a flowchart schematically showing a method of producing a conductive composite film of the present invention, and FIG. 2 is a schematic view of a method of manufacturing a conductive composite film of the present invention.

Hereinafter, a method for producing the conductive composite film of the present invention will be described in detail with reference to FIGS. 1 and 2. FIG.

First, the surface of the wafer is modified with a hydrophilic surface (step a).

More specifically, the surface of the wafer can be modified to a hydrophilic surface by treating it with an O ₂ plasma, thereby separating the wafer in step g below.

Next, the conductive nanowires are coated on the wafer (step b).

The conductive nanowire may be silver, gold, aluminum, copper, platinum, palladium, tin, carbon nanotubes (CNT) or the like, preferably silver nanowires.

Next, the conductive Nanowire  A solution containing a polymer is coated on the wafer to form a conductive Nanowire - polymer complex Laminated The laminate  (Step c).

The solvent of the solution may be toluene, chloroform, acetone or the like, preferably toluene.

Next, strain is applied to a stretchable substrate having the polymer formed on its surface, and a pre-strain-applied stretchable substrate is prepared (step d).

The polymer may be the same as the polymer of the above-mentioned laminate.

The stretchable substrate may be polydimethylsiloxane, polyurethane, or the like, preferably polydimethylsiloxane.

The strain may be smaller than a critical strain of the polymer layer included in the conductive composite film, and the critical strain may be calculated according to the following equation (1).

[Formula 1]

는 임계변형(critical strain),

는 신축성 기판의 모듈러스,

는 고분자층의 모듈러스이다.

Is a critical strain,

Modulus of the stretchable substrate,

Is the modulus of the polymer layer.

The strain may be from 0.01 to 1,000%, and preferably from 0.01 to 100%.

Next, In the laminate  Conductivity included Nanowire - polymer complex and the above free  And adheres so that the polymer contained in the stretchable substrate to which the strain is applied faces (step e).

A buckling phenomenon may occur depending on a direction in which the strain is applied, and the buckling phenomenon may buckle the conductive nanowire into a waveform including a valley and a floor.

Accordingly, the conductive nanowire is not broken even when a strain equal to or less than the strain is applied, so that conductivity is maintained and mechanical properties can be improved.

At this time, the buckling by the strain is selectively generated in the conductive nanowire having a high modulus, and the elastic substrate and the polymer may not buckle. Accordingly, scattering of light by the stretch substrate and the polymer does not occur, and the transmittance of the conductive composite film is not significantly reduced. The decrease in permeability due to buckling can be caused by the increase in the density of the conductive nanowires.

Next, the result of step (e) is heat treated (step f).

Finally, the resultant of step (f) is treated with a polar solvent to produce the conductive composite film from the result of step (f) (step g).

The polar solvent may be water, isopropyl alcohol, ethanol, propanol, butanol or the like, preferably water.

[Example]

Hereinafter, preferred embodiments of the present invention will be described. However, this is for illustrative purposes only, and thus the scope of the present invention is not limited thereto.

Preparation Example 1: Preparation of silver nanowire-coated film (film resistance: 30 ohm)

After the upper surface of the wafer (wafer beads) was subjected to O ₂ plasma treatment (22 sccm, 100 W, 1 minute), silver nanowire solution (ethanol dispersion 0.5 wt%, nano-pixice) was diluted to 0.1 wt% Spin coating to form a silver nanowire layer. (2 wt%) solution of SIS block copolymer (Styrene: isoprene = 15:85, KRATON D 1107, kraton polymer) dissolved in toluene on the silver nanowire layer was spin-coated at 2,000 rpm for 30 seconds to form a silver nanowire coating A film was prepared.

Production Example 2: Preparation of Silver Nanowire Coating Film

Silver nanowire coating film was prepared in the same manner as in Production Example 1, except that 0.01 wt% was used instead of 0.1 wt% of the nanowire solution.

Preparation Example 3: Preparation of silver nanowire-coated film (film resistance: 23 ohm)

Silver nanowire-coated films were prepared in the same manner as in Preparation Example 1 except that the nanowire solution was spin-coated five times instead of three times.

Production Example 4: Preparation of silver nanowire-coated film (film resistance: 14 ohm)

Silver nanowire coating film was prepared in the same manner as in Production Example 1, except that the nanowire solution was spin-coated 7 times instead of 3 times.

Example 1: Preparation of Conductive Composite Film

The SIS block copolymer solution (2 wt%) dissolved in toluene was spin-coated on the wafer at 2,000 rpm for 30 seconds to form a block copolymer thin film, and a PDMS film (thickness 1 mm, Dow HiTech) was prepared separately. Thereafter, both films were subjected to plasma treatment to be adhered and peeled off from the wafer to produce a laminate. After 50% strain was applied to the laminate, the top surface of the silver nanowire coating film prepared according to Production Example 1 and the block copolymer layer of the laminate were adhered to face each other. Next, the film was heat-treated at 90 ° C for 10 minutes and then placed in water to separate the wafer, thereby preparing a conductive composite film.

Example 2: Preparation of conductive composite film

A conductive composite film was produced in the same manner as in Example 1, except that a strain of 100% was applied instead of 50% of the strain to the laminate.

Example 3: Preparation of Conductive Composite Film

A conductive composite film was prepared in the same manner as in Example 1 except that a silver nanowire coating film prepared according to Production Example 3 was used in place of the silver nanowire coating film prepared according to Production Example 1. [

Example 4: Preparation of Conductive Composite Film

A conductive composite film was prepared in the same manner as in Example 1 except that a silver nanowire coating film prepared according to Production Example 4 was used in place of the silver nanowire coating film prepared according to Production Example 1. [

Example 5: Preparation of Conductive Composite Film

A conductive composite film was prepared in the same manner as in Example 1, except that a silver nanowire coating film prepared according to Production Example 2 was used in place of the silver nanowire coating film prepared according to Production Example 1.

[Test Example]

Test Example 1: SEM image of conductive composite film

3 is an SEM image of a conductive composite film produced according to Example 1. Fig.

Referring to FIG. 3, it was found that buckling occurred in a direction in which the silver nanowires were strained.

Test Example 2: Conductivity change according to strain of the conductive composite film

Fig. 4 is an optical microscope (OM) image after strain is again applied to the conductive composite film produced according to Example 1, Fig. 5 is a graph showing changes in resistance while applying strain again to the conductive composite film produced according to Example 2 .

Referring to FIG. 4, the conductive composite film produced according to Example 1 showed no breakage of silver nanowires in a strain of less than pre-strain (50%).

Referring to FIG. 5, the conductive composite film produced according to Example 2 showed almost no change in resistance even when strain was applied to the pre-strain (100%).

Therefore, it was found that the conductive composite film of the present invention had no breakage of the silver nanowire due to the strain applied before the pre-strain, and the reliability of the conductive composite film was improved because there was almost no change in conductivity.

Test Example 3: Measurement of transmittance of conductive composite film

FIG. 6 is a graph showing the results of a comparison between the silver nanowire coating film (water-removed wafer, black) prepared according to Production Example 1, Production Examples 3 and 4 and the conductive composite film (red) prepared according to Example 1, The results are shown in Fig. Fig. 6 (a) shows the results of measurement of Production Example 1 and Example 1, (b) of Production Example 3 and Example 3, and (c) of Production Example 4 and Example 4. Fig.

Referring to FIG. 6, it can be seen that the difference in transmittance before (black) and after (red) is very small, which is 2 to 4%. This is because buckling of the conductive composite film occurs selectively only in silver nanowires other than block copolymers.

Therefore, unlike the conventional conductive composite film, the conductive composite film of the present invention does not cause buckling in the block copolymer, so that scattering does not occur and the decrease in the transmittance is not significant.

Test Example 4: Confirmation of buckling according to the arrangement angle of silver nanowires

7 is an SEM image of a conductive composite film produced according to Production Example 2 (AgNW before transfer) and Example 5 (AgNW after transfer [50% prestrain]).

6, the silver nanowires are largely buckled in the direction of applying the strain (the left and right direction in the drawing), but the closer the angle to the direction in which the strain is applied becomes closer to 90 degrees (the up and down direction in the drawing) It was found that buckling occurred little or not.

Therefore, it was found that, as the silver nanowires included in the conductive composite film were arranged side by side with respect to the strain applying direction (lateral direction in the figure), buckling occurred to a large extent.

The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

Claims (17)

(a) modifying the surface of the wafer with a hydrophilic surface;
(b) coating the conductive nanowires on the wafer;
(c) coating a solution containing a polymer on the conductive nanowire to prepare a laminate in which a conductive nanowire-polymer composite is laminated on the wafer;
(d) preparing a stretchable substrate to which a pre-strain is applied by applying strain to the stretchable substrate on which the polymer is formed;
(e) bonding the conductive nanowire-polymer composite contained in the laminate to the polymer contained in the stretchable substrate to which the pre-strain is applied;
(f) heat treating the result of step (e); And
(g) treating the result of step (f) with a polar solvent to separate the wafer from the result of step (f) to produce a conductive composite film,
The conductive composite film
A stretchable substrate;
A polymer layer formed on the stretchable substrate;
And a corrugated conductive nanowire formed on the polymer layer,
Wherein said waveform is formed by buckling,
Wherein the strain is smaller than a critical strain of the polymer layer included in the conductive composite film,
A method for producing a conductive composite film. delete The method according to claim 1,
Wherein the buckling phenomenon occurs parallel to a plane direction of the stretchable substrate and along a predetermined direction. The method according to claim 1,
Wherein the stretchable substrate has a modulus of 0.01 Mpa to 20 Gpa. 5. The method of claim 4,
Wherein the polymer layer has a modulus of 0.01 Mpa to 10 Gpa. The method according to claim 1,
Wherein the stretchable substrate comprises at least one selected from the group consisting of polydimethylsiloxane and polyurethane. The method according to claim 1,
Wherein the polymer layer is a block copolymer layer. 8. The method of claim 7,
The block copolymer layer may be a poly (styrene-isoprene-styrene), a poly (styrene-butadiene-styrene), or a SEBS (poly (styrene- -propylene-styrene). < / RTI > The method according to claim 1,
Wherein the conductive nanowire comprises at least one selected from silver, gold, aluminum, copper, platinum, palladium, tin and carbon nanotubes (CNT). delete delete The method according to claim 1,
Wherein a buckling phenomenon occurs parallel to a direction in which the strain is applied. delete The method according to claim 1,
Wherein the strain is 0.01 to 1,000%. 2. The method of claim 1, wherein in step (a)
Wherein the surface of the wafer is treated with an O ₂ plasma to modify the surface to a hydrophilic surface. The method according to claim 1,
Wherein the polar solvent comprises at least one selected from the group consisting of water, ethanol, isopropyl alcohol, propanol, and butanol. A method for producing an electrode comprising the method of producing a conductive composite film according to claim 1.

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